backend_base.h

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// BSD 3-Clause License
// Copyright (c) 2025, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#pragma once
 
#include "database_backend.h"
#include "result.h"
#include "../database_types.h"
 
#include <kcenon/common/patterns/result.h>
 
#include <memory>
#include <atomic>
 
namespace database
{
namespace core
{
 
template<typename Derived, database_types Type>
class backend_base : public database_backend
{
public:
    backend_base() = default;
 
    ~backend_base() override
    {
        shutdown();
    }
 
    // Prevent copying (backends own unique resources)
    backend_base(const backend_base&) = delete;
    backend_base& operator=(const backend_base&) = delete;
 
    // Prevent moving (std::atomic members are not moveable)
    backend_base(backend_base&&) noexcept = delete;
    backend_base& operator=(backend_base&&) noexcept = delete;
 
    static std::unique_ptr<database_backend> create()
    {
        return std::make_unique<Derived>();
    }
 
    database_types type() const override
    {
        return Type;
    }
 
    kcenon::common::VoidResult initialize(const connection_config& config) override
    {
        if (initialized_) {
            return kcenon::common::error_info{
                static_cast<int>(database::error_code::invalid_state),
                "Backend already initialized",
                Derived::backend_name()
            };
        }
 
        auto result = static_cast<Derived*>(this)->do_initialize(config);
        if (result.is_ok()) {
            initialized_ = true;
        }
        return result;
    }
 
    kcenon::common::VoidResult shutdown() override
    {
        if (!initialized_) {
            return kcenon::common::ok();
        }
 
        auto result = static_cast<Derived*>(this)->do_shutdown();
        initialized_ = false;
        return result;
    }
 
    bool is_initialized() const override
    {
        return initialized_;
    }
 
protected:
    std::atomic<bool> initialized_{false}; 
};
 
} // namespace core
} // namespace database